Science

From boarding a train to filling a glass of water, we depend on a whole network of critical infrastructure systems which work invisibly in almost every part of our lives.

But as more and more people come to rely on these networks, they become increasingly fragile—when a single fallen tree can cause a whole country to lose power for hours, it’s clear we need to improve our systems.

Some of Dr Latty’s research has been focused on the Argentine ant—one of the world’s top 100 most dangerous invasive species. When Argentine ants move in, they generally kill all of the native species of ants in the area.

The Argentine ant is not the big red ant in this picture – it’s the three smaller ants trying to murder it.

But Dr Latty’s interest lies in the remarkable transportation networks that Argentine ants make. Instead of having one central nest, Argentine ants have multiple nests that make up a colony, not unlike towns in a country—all interacting, yet distinct—and they link these up not only with each other, but with food sources.

And some of these colonies are enormous. The European Argentine Ant supercolony is thought to span six thousand kilometres, passing through Portugal, Spain, France and Italy.

For the transportation networks between these nests to work this well, they have to be efficient.

“Whenever an ant is above ground, it’s dangerous—things could eat it, it can get stepped on, it can get dried out in the sun,” Dr Latty explains.

When her team placed a group of Argentine ants into an empty arena with three nests, they found the ants were able to create the most efficient network connecting the three points — in mathematics, this is called a Steiner tree.

This is certainly remarkable, considering that an ant’s brain is about the size of a grain of sand, and even more remarkable when Dr Latty admits that Argentine ants are “probably the dumbest species” she’s ever worked with.

“If you put them into a T-maze, and the only thing they need to learn is that you turn left for food, they don’t learn it,” she says. “But, if you take thousands of them, put them into this situation, all of a sudden they’re solving shortest path problems.”

How does the Argentine ant manage this?

Well, when the ants walk, they lay down a trail of attractive chemicals—called pheromones—to mark the path for other ants. As more ants find the efficient route, these pheromone trails become more concentrated, and thus more attractive to other ants, reinforcing the shortest path until the pheromones on all the other less efficient trails have evaporated.

But these efficient networks are not very resilient. Because these trails are just made up of pheromones, it doesn’t take much to restructure them.

“If you have a self-healing trail system, there’s not a lot of reason to build resilience into it,” says Dr Latty.

A species that invests a little more into its networks may provide a better model for human systems.

The Australian meat ant, for example, spends a lot of time and energy clearing grass to create trails which are sometimes so pronounced that they can be seen on Google Earth.

Meat ant trail network, as seen from above

Analysing maps of meat ant colonies, Dr Latty found that meat ant networks strike the balance between resilience and being cheap.

Swedish mathematician Arianna Botinelli worked with Dr Latty to create mathematical rules that mimicked the patterns of meat ant trail construction. With a little bit of tweaking, these rules could be applied to human systems of thousands of points to create balanced networks.

The other organism that Dr Latty works with is perhaps more bizarre: the acellular slime mould—a completely brainless, single-celled organism which she describes as a “motile blob of goo.”

If you cut a slime mould into pieces, each of those pieces will become a fully independent individual within minutes, and if you put all of those pieces back together again, they’ll “very happily” reorganise themselves back into a single individual.

In 2010, a researcher from Hokkaido University in Japan placed a slime mould on a map of Tokyo with oat flakes (which slime moulds eat) marking all of the major destinations. After 26 hours, the slime mould had formed itself into a network almost identical to the Tokyo rail network.

“This is an organism that doesn’t even have a brain, it has no neurons, no organs.”

Since then, this experiment has been recreated for transportation networks all over the world with oat flakes marking high population centres and light, which slime moulds hate, used to represent mountain ranges or other geographical obstacles.

Every time, the slime mould has created networks that are just as efficient as the human ones—with the exception of America, where the slime mould’s network was actually more efficient.

“It seems that whatever the slime mould is trying to optimise is pretty much the same thing as human engineers are trying to do. The difference is that human engineers have giant brains, access to computers and hundreds of years of history in designing networks — the slime mould is basically just moving mucous.”

“There are scientists now working on trying to figure out how the slime mould does this, so we can apply it to our own systems.”

Dr Latty thinks of nature as “a big toolbox of solutions—22,000 ants, 900 known species of slime mould, and they’re all doing slightly different things.”

“If you want to build a cheap network, if the goal is to solve a shortest path problem, well the Argentine ants are a great place to start,” she says. “If you want to build a balanced network, talk to the meat ants.”

“We can look at what ants are doing, we can draw inspiration from that, we can get ideas that we might not normally have had and then we can use our big brains, which is our big asset, to tweak those into solutions that work for us.”